In the processes and equipment known to date, the thermoplastic material contaminated by admixtures was heated and squeezed through a screen by means of a piston. Other methods are known also. The disadvantage of all of these methods is always that it is difficult to transport the admixtures away. The material to be processed must be subjected to pressure and heat but its viscosity is high, and in the course of the reprocessing the percentage of admixtures becomes greater and greater and the percentage of the thinly liquid material smaller and smaller, which necessitates higher and higher processing pressures. This results in much wear of the machinery, e.g. of the screens and the pistons, and the process itself becomes rather uneconomical because it cannot be carried out continuously as screens have to be cleaned constantly, admixtures removed separately, causing long processing interruptions. Accordingly, the known methods with their equipment are not very economical overall because the equipment wears quickly, is subject to very high compressive stresses and, in relation to the material to be reprocessed, the yield is not high enough, i.e. the contaminations to be discarded still contain a relatively large amount of usable material.